Hand-held cutting tools or instruments used to cut a variety of objects are known in the art. For example, a pair of scissors or shears is a hand-held cutting tool used to cut relatively softer types of materials such as paper, plastics or cloth and the like. This type of hand-held cutting tool is particularly useful for cutting materials that offer very little resistance to being cut, and thus require very little force to initiate a cut. These cutting tools, however, are of limited application and are not well suited for cutting hard objects such as metals or ceramics and the like that require a greater degree of force to initiate the cutting operation.
Hand-held cutting tools that are used to cut harder materials are configured differently from those used to cut the relatively softer materials, and are usually made from a harder material in order to endure repeated cuts. For example, a hand-held cutting tool used to cut through metal wire is configured similar to a pair of pliers having the characteristic handle and jaw arrangement. However, unlike pliers, this type of cutting tool comprises a pair of opposed cutting edges instead of opposed gripping members. The cutting tool configuration is dictated by the large force that must be applied to the cutting edges to cut a hard metal object. The tool's long handles and hinged jaw arrangement positioned near the opposed cutting edges facilitates the transfer of force needed to cut through a hard metal object.
Such hand-held cutters are known in the art and are used in a variety of manufacturing applications as well as medical and dental applications where hard materials must be cut with some degree of precision. In the area of electronics manufacturing, such cutting tools are used to cut metal wires used for making critical electrical connections and the like. In in the area of orthodontics, such cutting tools are used to make precision cuts through orthodontic arch wire used with orthodontic brackets for straightening teeth. A cutting tool used in such a manufacturing, dental or medical application must possess characteristics that exceed those of cutting tools used to perform cuts on hard materials in other less exacting applications.
A cutting tool that is used in a medical or dental procedure must operate smoothly to enable the user to make a precise cut during each use. The cutting edge of the tool must be capable of retaining its sharpness, permitting the user to use the tool repeatably without loss of cutting ability. The cutting tool must also be capable of withstanding repeated sterilizations without adversely affecting the tool's performance ability and preferably without affecting its appearance.
Hand-held cutting tools that are used in medical, dental, or high quality manufacturing applications for cutting hard materials are known in the art. Such cutting tools are configured in the plier-like arrangement for the purpose of transferring to the cutting edge of the tool the amount of force required to cut hard materials. The cutting tool is manufactured from stainless steel to enhance resistance to corrosion during repeated use and sterilization. However, stainless steel is a relatively soft metal that does not hold up well to the repeated cutting of hard metals. Therefore, cutting tools made from stainless steel are known to contain hardened tool-steel inserts that serve as the cutting edge. The hardened tool-steel inserts permit the tool to make repeated cuts of hard materials without requiring frequent sharpening.
In the past, such a cutting tool would permit a user to make repeated cuts of relatively hard materials after repeated sterilizations without a significant loss in the tool's performance capabilities. However, in today's society and the heightened awareness of AIDS and the HIV virus, tools and instruments used during any medical or dental procedure must now undergo more extensive sterilization than ever before. In the past, it was sufficient that tools or instruments used for relatively minor dental or medical procedures only undergo a cold sterilization that consisted of simply wiping or soaking the instrument with isopropyl alcohol and the like.
Today, however, a tool or instrument used during any medical or dental procedure must undergo an extensive sterilization process similar to that mandated under FDA regulations for a tool or instrument used during a surgical procedure. The newly mandated FDA sterilization procedures require that the tool or instrument be subjected to high temperature autoclaving, chemical claving, or dry heat treatment. Accordingly, cutting tools used during medical or dental procedures must now be capable of retaining their ability to perform precise cuts after repeated uses and sterilization under the new more extreme sterilization procedures.
The development of new technologies has also permitted the use of new metal compositions that are much harder than those metal compositions known before. Many of these new metal compositions are finding medical and dental application due to their unique physical properties. Therefore, cutting tools that are used during medical or dental procedures incorporating such new metal compositions must possess increased hardness enabling the cutting tool to preform repeated cuts without loss of cutting ability.
The hand-held cutting tools known in the art preform adequately when used to cut old-technology metals after being subjected to the old cold method of sterilization. However, these tool do not retain their cutting performance when subjected to the repeated cutting of new technology metals and the more extreme methods of sterilization. Typical new technology metals used in dental or medical applications have a Rockwell C hardness of approximately 50 to 60 which is only slightly less than that of the hardened tool-steel inserts forming the tool cutting edges. Therefore, each use of the tool adversely affects the sharpness of the cutting edges, and thus the ability to perform repeated precision cuts without frequent sharpening.
In addition, stainless steel cutting tools known in the art also display high instances of corrosion after being subjected to repeated sterilizations under the newly mandated procedures. This corrosion makes the tool unfit for use in manufacturing, medical and dental applications because it ultimately impairs the tool operation and its ability to perform a precision cut. Additionally, the continued use of a corroded cutting tool in a dental or medical application may pose the threat of contamination or infection through contact with an open incision.
Corrosion occurs throughout the surface of the cutting tool. However, the corrosion most notably affects the interactive movement of the tool's cutting members and the cutting edge of the tool itself. Corrosion causes the once smooth and precise interactive movement of the tool's cutting members to bind during the cutting operation, making the tool difficult and awkward to operate.
Corrosion along the hardened steel cutting edges causes them to deteriorate, adversely affecting the tool's ability to cut. Although the life of the cutting tool may be extended by frequent sharpening, this is inconvenient because it prevents the user from using the tool while it is returned to the manufacturer to be sharpened. Also, a higher likelihood exists that the tool will inadvertently be used after it is dull when the tool is one requiring frequent sharpening. The potential harm that could result from using a dull cutting tool to initiate a cut where precision is called for outweighs the utility of a cutting tool requiring frequent sharpening. Finally, the extent of such sharpening is ultimately limited by the thickness of the hardened metal coating.
In an attempt to increase the cutting tool's corrosion resistance and enhance the hardness of its cutting edge, cutting tools have been known to be plated with hard chrome. Hard chrome is selected as the plating material because of its characteristic hardness and ability to resist corrosion. In practice, cutting tools plated with hard chrome display better corrosion resistance throughout the body of the tool than plain stainless steel cutting tools. However, cutting tools plated with hard chrome are unable to retain their coating at the cutting edge where such corrosion resistance and enhanced hardness is critical. Shortly after use, the hard chrome plating at the cutting edge of the tool flakes off and away from the cutting edge leaving exposed the bare hardened tool-steel insert. The hard chrome flaking is believed to be caused by the lack of surface area at the tip of the cutting edge necessary for adherence. After the hard chrome plating has flaked away, the cutting edge undergoes corrosion that causes the cutting edge to deteriorate, adversely affecting the sharpness of the cutting edge and the tool's ability to cut.
Once the hard chrome plating has flaked away from the cutting edge, repeated use and sterilization of the tool causes corrosion to form underneath the remaining hard chrome plating, causing the stainless steel body of the tool to deteriorate. As the corrosion progresses, there exists the additional danger of contamination or bodily infection that may result from the hard chrome plating flaking off and falling into an open incision during a medical or dental procedure.
It is, therefore, desirable to provide a hand-held cutting tool for use in medical, dental, or high quality manufacturing applications having a cutting edge with enhanced hardness to permit its repeated use with metals, ceramics or other material compositions having a high hardness. It is also desirable that the cutting tool have enhanced corrosion resistance throughout its surface and at its cutting edge enabling the tool to withstand repeated sterilizations under the more extreme FDA mandated conditions.
The hand-held cutting tool should be capable of precise operation enabling a user to make precision cuts with the tool. Finally, the cutting tool should be manufactured by known commercial methods permitting cost effective production and sales of the product.